Slotted antenna system and method

ABSTRACT

A directional antenna is disclosed that includes an inner conductor positioned within an outer conductor. The directional antenna includes multiple slots around the periphery of the antenna and efficiently dissipates energy received at the slot, and is able to generate a directional azimuth pattern.

FIELD OF THE INVENTION

[0001] The present invention relates generally to antenna systems. Moreparticularly, the present invention is directed to a high powerdirectional slotted coaxial antenna and method.

BACKGROUND OF THE INVENTION

[0002] There are a number of stations that have been assigned a pair ofchannels, consisting of one National Television System Committee (NTSC)channel and one digital (DTV) channel, that require the station totransmit both NTSC and DTV channels at their maximum effective radiationpower (ERP), for example, 5 megawatt (MW) for NTSC channels and 1 MW forDTV channels.

[0003] Often, it is an objective to direct transmission of NTSC and DTVsignals in a particular direction. Conventionally, single-slot coaxialantennas, which have a single slot cut into the wall of the antenna, areutilized to transmit directional signals. When directional signals aretransmitted, the majority of signal power is transmitted in onedirection, and “skull” or “cardioid” shaped azimuth patterns aregenerated.

[0004] However, conventional single-slot antennas are at least sometimesnot successful in transmitting high power signals, in particular, twohigh power channels, such as a 5 MW NTSC channel and a 1 MW DTV channel,at the same time. Conventional single-slot antennas are at leastsometimes unable to adequately dissipate the amount of energy that isattributed to the pair of channels.

[0005] “Q” is a ratio that characterizes the amount of energy that isstored at a slot of an antenna versus the amount of energy that isdissipated by the slot. Ideally, an antenna operates more efficientlywhen it avoids the storing of energy. Typically, the higher the “Q” of aslot, the less power the slot of the antenna is able to handle. If theamount of energy stored at a slot becomes excessive, the air between theslot may begin to ionize, and the slot may function improperly.

[0006] It is known in the art that coaxial antennas with multiple slotshave a lower “Q” per slot. In general, the more slots cut into a coaxialwall of an antenna layer, the more the antenna is able to dissipate theenergy it receives. However, coaxial antennas with multiple slots havetraditionally been utilized to generate omni-directional azimuthpatterns. When more than one slot is cut into a layer of conventionalcoaxial antenna, the coaxial antenna will transmit energy, substantiallyevenly, in more than one direction. While conventional multiple-slottedcoaxial antennas are successful in reducing the “Q” of an antenna, theyhave generally not been successful in transmitting directional signals.

[0007] Accordingly, it would be desirable to provide an antenna thatavoids at least to some extent the storing of energy at a slot.

[0008] It would also be desirable to provide an antenna that is capableof transmitting high power NTSC and DTV channels simultaneously.

[0009] It would also be desirable to provide a directional slottedantenna.

SUMMARY OF THE INVENTION

[0010] The foregoing needs are met, to a great extent, by the presentinvention, wherein in one aspect an apparatus and method is providedthat in some embodiments provides a slotted antenna that is capable oftransmitting high power NTSC and DTV channels simultaneously, and thatat least to some degree avoids the storing of energy at a slot.

[0011] In one aspect of the present invention, a directional slottedantenna is provided that includes an outer conductor, and innerconductor positioned within the outer conductor, and a first slot and asecond slot positioned around a peripheral of the outer conductor. Thefirst slot and the second slot form a first layer of the slottedantenna. Energy transmitted due to the first slot and the second slotgenerates a directional azimuth pattern from the directional slottedantenna.

[0012] In another aspect of the present invention, a method ofassembling a directional antenna that includes positioning an innerconductor within an outer conductor, and positioning a first and secondslot around a periphery of the outer conductor on a first layer of thedirectional antenna.

[0013] In another aspect of the present invention a directional slottedantenna system is provided that includes a means for feeding a signal toa first slot, a means for coupling the signal from the feeding means tothe first slot, and a means for establishing a first potentialdifference across the first slot and a second potential differenceacross a second slot, such that a directional azimuth pattern isgenerated from the directional antenna system.

[0014] In yet another aspect of the present invention a directionalslotted antenna is provided that includes an outer conductor and a firstslot and a second slot positioned around the peripheral of the outerconductor. The directional slotted antenna generates a directionalazimuth pattern.

[0015] There has thus been outlined, rather broadly, the more importantfeatures of the invention in order that the detailed description thereofthat follows may be better understood, and in order that the presentcontribution to the art may be better appreciated. There are, of course,additional features of the invention that will be described below andwhich will form the subject matter of the claims appended hereto.

[0016] In this respect, before explaining at least one embodiment of theinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The invention is capable of otherembodiments and of being practiced and carried out in various ways.Also, it is to be understood that the phraseology and terminologyemployed herein, as well as the abstract, are for the purpose ofdescription and should not be regarded as limiting.

[0017] As such, those skilled in the art will appreciate that theconception upon which this disclosure is based may readily be utilizedas a basis for the designing of other structures, methods and systemsfor carrying out the several purposes of the present invention. It isimportant, therefore, that the claims be regarded as including suchequivalent constructions insofar as they do not depart from the spiritand scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a cross-sectional view of a slotted coaxial antenna inaccordance with the present invention, taken through line 1-1 in FIG. 2.

[0019]FIG. 2 is a perspective view of the slotted coaxial antenna ofFIG. 1.

[0020]FIG. 3 is a graphical representation of a cardioid-shaped azimuthpattern.

[0021]FIG. 4 is a multi-layer slotted coaxial antenna in accordance withthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0022] The invention in some embodiments provides a slotted antenna thatis capable of transmitting high power NTSC and DTV channelssimultaneously, and that at least to some degree avoids the storing ofenergy at a slot. The invention will be described with reference to thedrawing figures, in which like reference numerals refer to like partsthroughout. One embodiment of the present invention provides amulti-slotted antenna having an inner conductor positioned within anouter conductor, and a first slot and a second slot positioned aroundthe peripheral of the outer conductor that form a first layer of theantenna. When energy is transmitted from the multi-slotted antenna, dueto the first and second slots, a directional azimuth pattern isgenerated from the multi-slotted antenna.

[0023] The multi-slotted antenna may be utilized to transmit directionalsignals, and is capable of transmitting high power signals, for example,a 5 MW NTSC channel and a 1 MW DTV channel simultaneously. Moreover, themulti-slotted antenna of the present invention efficiently stores anddissipates energy at a slot.

[0024] Shown in FIG. 1 is a cross-sectional view of a multi-slottedantenna 10, in accordance with the present invention. The design of theantenna 10 includes an inner conductor 12 positioned within an outerconductor 14. Multiple slots 16, 18, 20 and 22 are positioned around theperipheral of the outer conductor 14. In a preferred embodiment of thepresent invention, the inner conductor 12 and the outer conductor 14 arecoaxial, and there are four slots 16, 18, 20 and 22 for each layer ofthe antenna 10.

[0025] Two of the slots, slots 16 and 20, are directly coupled slotsthat are referred to as non-parasitic slots. Slot 16 is directly coupledvia couplers 24 and 26, and slot 20 is directly coupled via slots 28 and30. The other two of the slots, slots 18 and 22, are indirectly coupledslots and are referred to as parasitic slots. Slot 18 is indirectlycoupled via couplers 24 and 26, and slot 22 is indirectly coupled viacouplers 28 and 30. Each of the non-parasitic slots have one of couplers24-30 positioned at each end of the respective slots, and first andsecond coupler pairs 32, 34 are formed. The parasitic slots 18 and 22 donot have a coupler positioned immediately at each end. Fins 36, 38 arecoupled to the outer conductor 14.

[0026]FIG. 2 is a perspective view of one layer of antenna 10. As shownin FIG. 2, one coupler 24 of the coupler pair 32 is positioned at aheight along a y-axis that is above the other coupler 26, such that apotential difference across the slot 16 is created.

[0027] During operation, the couplers 24,26,28 and 30 couple the signalpower from the inner conductor 12 to the outer conductor 14. The firstcoupler pair 32 creates a first potential difference across the firstnon-parasitic slot 16 and a second potential difference across the firstparasitic slot 18.

[0028] The potential differences established across slots 16 and 18cause currents to radiate from the outer conductor 14. However, thecurrent generated due to the first parasitic slot 18 will be less thanthe current generated due to the first non-parasitic slot 16, as thecouplers 24, 26 of the coupler pair 32 are further from the ends of theparasitic slot 18. As a result, the second potential difference acrossthe parasitic slot 18 is less than the first potential difference acrossthe non-parasitic slot 16. It should be understood that the firstcoupler pair 32 may create a potential difference across slots 20 and22. However, the effect of the potential difference on the resultingazimuth pattern is minimal in some embodiments.

[0029] Similarly, the second coupler pair 34 creates a third potentialdifference across the second non-parasitic slot 20 and a fourthpotential difference across the second parasitic slot 22. The potentialdifferences established across slots 20 and 22 cause currents to radiatefrom the outer conductor 14. However, the current generated due to thesecond parasitic slot 22 is less than the current generated due to thesecond non-parasitic slot 20, as the couplers 28, 30 of the secondcoupler pair 34 are further from the ends of the parasitic slot 22. As aresult, the potential difference across the parasitic slot 22 is lessthan the potential difference across the non-parasitic slot 20. Itshould be understood that the second coupler pair 34 may also create apotential difference across slots 16 and 18. However, the effect of thepotential difference on the resulting azimuth pattern is minimal in someembodiments.

[0030] Unlike a conventional multi-slotted antenna that only transmitsomni-directional signals, an antenna in accordance with the presentinvention is a multi-slotted antenna that may be utilized to transmitdirectional signals. Accordingly, an antenna 10 in accordance with thepresent invention is able to generate a “cardioid” or “skull” shapedazimuth pattern that is indicative of the transmission of directionalsignals.

[0031] In addition, the use of directly and indirectly coupled slotsalso referred to herein as non-parasitic and parasitic slots,respectively, accomplishes proportional distribution of the coupledsignal power between slots 16 and 18 and also, between slots 20 and 22.

[0032] As a result, the distribution of the signal power that istransmitted from the antenna is controlled. Thus, more signal power istransmitted from the non-parasitic slots 16, 20 due to the greatercurrents generated by the non-parasitic slots 16, 20, than the parasiticslots 18, 22. Accordingly, a directional azimuth pattern, where moreenergy is distributed in one direction than another, is generated fromthat layer of the antenna 10.

[0033] The fins 36, 38 may also be utilized to shape the resultingazimuth pattern. A directional azimuth pattern may also be shaped byselecting, for example, the coupler sizes, the number of slots, the sizeof the slots, the length of the slots, the positioning of the parasiticslots, and/or the positioning of fins that are positioned around theperipheral of the outer conductor.

[0034] Moreover, the antenna in accordance with the present invention,while benefiting from the ability of a multi-slot configuration todistribute energy among more than one slot can avoid the generation ofan omni-directional azimuth pattern and produce a directional azimuthpattern. Accordingly, the antenna in accordance with the presentinvention, avoids the storing of energy at one slot and reduces the “Q”associated with a single-slot antenna.

[0035] Shown in FIG. 3 is a directional azimuth pattern 38 generatedfrom an antenna 10 in accordance with the present invention. As shown inFIG. 3, the proportion of the energy distributed in the upper half 40 ofthe azimuth pattern 38, which, in this example, corresponds to thelocation of the directly coupled, non-parasitic slots 16, 20, is greaterthan the proportion of the energy distributed in the lower half 42 ofthe azimuth pattern 38, which corresponds to the indirectly coupled,parasitic slots 18, 22.

[0036] Advantageously, the proportional distribution of energy betweenthe non-parasitic slots 16, 20 and their corresponding parasitic slot18, 22 remains constant for each layer of an antenna 10 having the samenon-parasitic and parasitic slot configuration. As a result, theproportion of signal power transmitted from layer to layer stays thesame and a directional azimuth pattern 38 can be maintained for eachlayer of the antenna. Thus, if the antenna requires an adjustment withthe amount of energy that is coupled to the outer conductor 14, forexample, to accomplish beam tilting, the proportion of signal powertransmitted will remain equal, as long as the length of the parasiticslots remain equal for each layer of the antenna 10. The length of theparasitic slots do not have to be equal to each other, but have to beequal to the corresponding parasitic slot of another layer, which is inthe same position relative to the periphery of the outer conductor 14,to maintain a directional azimuth pattern with an equal radiation ratiofor each layer of the antenna. Accordingly, a directional azimuthpattern 38 will be generated for each layer of the antenna 10. Thedesired radiation ratio will remain equal and independent of the size ofcouplers 24, 26, 28 and 30 or the slot length of the non-parasitic slots18, 20.

[0037] In a preferred embodiment of the present invention, the amount ofsignal power transmitted due to the parasitic slots 18, 22 is one-fourthof the amount of signal power transmitted due to the non-parasitic slots16, 20. However, other ratios can alternatively be employed.

[0038] Shown in FIG. 4 is an embodiment of a multi-layer slotted coaxialantenna 44 in accordance with the present invention. The slotted coaxialantenna of FIG. 4 has a first layer 46, a second layer 48, a third layer50, and a fourth layer 52. Each layer may transmit signals that havedifferent amplitudes and phases to shape a desired elevation pattern forthe antenna. It is not uncommon to vary the size of the couplers at thedirectly coupled slots or the slot length of the directly coupled slotsto vary the amplitude and phase of a signal transmitted from each layerof an antenna. However, as long as the length of a parasitic slotremains equal to the length of a parasitic slot of other layers 46, 48,50, 52 that are in the same position relative to the periphery of theouter conductor 14 of the antenna 44, a directional azimuth pattern willbe generated for each layer 46, 48, 50, 52 of the antenna 44, and theradiation ratio will be the same, or substantially the same, for eachlayer 46, 48, 50, 52 of the antenna 44.

[0039] The many features and advantages of the invention are apparentfrom the detailed specification, and thus, it is intended by theappended claims to cover all such features and advantages of theinvention which fall within the true spirit and scope of the invention.Further, since numerous modifications and variations will readily occurto those skilled in the art, it is not desired to limit the invention tothe exact construction and operation illustrated and described, andaccordingly, all suitable modifications and equivalents may be resortedto, falling within the scope of the invention.

What is claimed is:
 1. A directional slotted antenna, comprising: anouter conductor; an inner conductor positioned within the outerconductor; and a first slot and a second slot positioned around aperiphery of the outer conductor forming a first layer of thedirectional slotted antenna, wherein energy transmitted via the firstslot and the second slot generates a directional azimuth pattern fromthe directional slotted antenna.
 2. The antenna of claim 1, furthercomprising a fin coupled to the outer conductor.
 3. The antenna of claim1, wherein the directional slotted antenna transmits an NTSC and a DTVchannel simultaneously.
 4. The antenna of claim 3, wherein the NTSCchannel is a 5 MW channel and the DTV channel is a 1 MW channel.
 5. Theantenna of claim 1, further comprising: a first coupler positioned at afirst end of the first slot; and a second coupler positioned at a secondend of the first slot.
 6. The antenna of claim 5, wherein the firstcoupler and the second coupler couple energy from the inner conductor tothe first slot and establishes a first potential difference across thefirst slot, and a second potential difference across the second slotthat is less than the potential difference across the first slot.
 7. Theantenna of claim 5, wherein a bottom of the first coupler is positionedat a height on a y-axis that is greater than a position along the y-axisof a top of the second coupler.
 8. The antenna of claim 5, wherein afirst length of the second slot determines the proportion of energycoupled to the second slot.
 9. The antenna of claim 5, wherein a ratioof radiated power between the first slot and second slot is equal. 10.The antenna of claim 5, further comprising: a third slot and a fourthslot positioned around the peripheral of the outer conductor.
 11. Theantenna of claim 10, further comprising: a third coupler positioned at afirst end of the third slot; and a second coupler positioned at a secondend of the third slot.
 12. The antenna of claim 11, wherein the thirdcoupler and the fourth coupler couple energy from the inner conductor tothe third slot, and establishes a third potential difference across thethird slot, and a fourth potential difference across the fourth slotthat is less than the potential difference across the third slot.
 13. Amethod of assembling a directional antenna, comprising: positioning aninner conductor within an outer conductor; and positioning a first andsecond slot around a periphery of the outer conductor on a first layerof the directional antenna.
 14. The method of claim 13, furthercomprising controlling a first ratio of radiated power between the firstslot and the second slot according to a slot length of the second slot.15. The method of claim 13, further comprising: positioning a firstcoupler at a first end of the first slot; and positioning a secondcoupler at a second end of the first slot.
 16. The method of claim 13,further comprising: positioning a third slot and a fourth slot aroundthe periphery of the first layer.
 17. The method of claim 16, furthercomprising: positioning a third coupler at a first end of the thirdslot; and positioning a fourth coupler at a second end of the thirdslot.
 18. The method of claim 13, further comprising forming a secondlayer of the directional antenna by positioning a fifth slot and a sixthslot around the peripheral of the outer conductor.
 19. The method ofclaim 18, wherein a second ratio of radiated power between the fifthslot and the sixth slot equals the first ratio of radiated power.
 20. Adirectional antenna system, comprising: means for feeding a signal to afirst slot; and means for coupling the signal from the feeding means tothe first slot; and means for establishing a first potential differenceacross the first slot and a second potential difference across a secondslot such that a directional azimuth pattern is generated from thedirectional antenna system.
 21. A directional slotted antenna,comprising: an outer conductor; and a first slot and a second slotpositioned around the periphery of the outer conductor, wherein thedirectional slotted antenna generates a directional azimuth pattern.